The US GPS and China's Beidou are both global satellite navigation systems, but the number of satellites they use differs. The US GPS only needs 24 satellites to cover the whole world, while China's Beidou needs more than 50 satellites to achieve the same coverage. Why is that?
First, we need to understand how a global navigation satellite system works. Global navigation satellite systems provide positioning services by sending radio signals to users on the ground. These satellites operate at an altitude of about 20,000 kilometers above the Earth, and they all follow the same orbit. When a user receives a signal from at least four satellites, they can determine their position by measuring the transmission time of the signal.
So why does the US GPS only need 24 satellites?This is because these satellites are evenly distributed on Earth, forming a complete constellation. Each satellite has its own number, and they orbit over the Earth at predetermined intervals. In this way, regardless of the user's location, they will be able to receive signals from at least four satellites and thus determine their own position.
However, the situation of China's Beidou is different. Since China's Beidou system also provides services such as short messages, search and rescue enhancements, and precise single-point positioning, more satellites are needed to support these functions. In addition, China Beidou has also adopted a hybrid technology for medium and high orbits, which can better meet the needs of users for positioning accuracy and coverage.
Specifically, the mixed distribution of medium- and high-orbit satellites in China's Beidou system, among which the number of medium-orbit satellites is large, can better achieve global coverageHigh-orbit satellites, on the other hand, are able to provide more precise positioning accuracy. This hybrid technology allows the China Beidou system to better adapt to the needs of different users, and can provide better positioning services in different scenarios.
In general, although the US GPS and China's Beidou are both global satellite navigation systems, the number of satellites they use differs. This is because different system designs and service requirements lead to different constellation layouts and satellite number configurations. However, no matter how many satellites are used, these systems are able to provide users with accurate and reliable positioning services.